1. Field of the Invention
This invention relates to gear trains, more particularly to an adjustable bevel gear train including a plurality of intermeshing bevel gears.
2. Prior Art
Gear trains involving a plurality of intermeshing bevel gears are known to the art. One particular application is found in industrial robots wherein the drive to the hand spindle is by means of a drive train which controls the point of application of the grasped load from a relatively remote point. The power transmission is, therefore, by means of shafts and gear units. In such constructions, a relatively large play can occur at the point of load application as a result of gear wear occurring over periods of use. In order to obtain the original precision of the robot, the play has to be corrected.
Elimination of gear play has heretofore been accomplished through the use of removable or insertable shims located within the gear train. When a bevel gear train has been utilized, one of the bevel gears has been provided with axial shims interposed between the gear and its housing mount. These axial shims can be changed in such a manner as to change the effective axial position of the gear, thereby allowing play to be taken up.
However, in order to change the axial position of the gear by means of a shim positioning, it is necessary to extensively disassemble the unit. This disassembly takes a considerable period of time and must be done by highly trained personnel. Additionally, because the shims have to be placed after removal of the shimmed gear, there is no guarantee that the correct technical adjustment will be made. As a consequent thereof, the timing of individual play corrections is often extended, partially due to lack of time in which to make the correction, and thus, the industrial robot is operated with increased play and results in increased imprecision such that the quota of rejected parts for the goods being handled by the robot is increased.
It would, therefore, be an advance in the art to provide a bevel gear train which is easily adjustable for the purpose of eliminating play between the gears.